Electromagnetically-operating loud-speaking device



July 0, 1929, L. sHAPmo 1,720,008

ELECTROMAGNETICALLY OPERATING LOUD SPEAKING DEVICE 9 A TToRNEvs.

July 1929. L SHAPIRQ n 1,720,008

ELECTROMAGNETIGALLY OPERATING LOUD SPEAKING DEVICE INVENToR. 77 A ZAfw/J SHA/wm w/ nvt-J3 L. sHAPlRo 1,720,008 ELECTROMAGNETICALLY OPERATING LOUD SPEAKING DEVICE Filed May 28, 1925 3 Sheets-Sheet 5 vn flaaanlllaalaa'llpa 11 r ,l I 1 IN V EN TOR. AZ/1R05 JHAP/Ro BY .i

W/T/VESS g4@ Patented July 9, 1929.

UNITED STATES PATENT OFFICE.

LAZAEUS SHAPRO, OF NEW YORK, N. Y., ASSIGNOR TO FREED-EISEMANN RADIO COR- PORATION, OF BROOKLYN, NEW YORK, A CORPORATION 0F NEW YORK.

ELECTROMAGNETICALLY-OPERATING LOUD-SPEAKING DEVICE.

Application med may 2s,

My invention relates more particularly to loud speakers, especially of the so-called cone type in which the sound vibrations are directly transmitted to the surrounding air without the use of a horn or similar loading device usually employed with ordinary vibrating diaphragm loud speakers, thecone acting directly as the sound radiator.

My improvements relate to particular features in the electromagnetic unit as will appear from the following description.

In the drawings- Figure 1 lrepresents a transverse vertical central section thru the entire loud speaker except the operating unit which is shown in side view;

Figure 2 represents in larger scale a small section of the rear rim portion of the cone showing the manner in which itis suspended on its support;

Figure 3 represents a transverse section thru a suspension lug;

Figure 4 represents in longitudinal section and in larger scale the apex portion of the cone Figure 5 represents a transverse section thru the cone chuck'on the line 55, in Figure 4;

Figure 6 represents in larger scale a longitudinal section thru the operating unit on the line 6-6, in Figure 7;

Figure 7 represents a view of the unit shown in Figure 6 seen from the right-hand `side, with the right-hand shank of the permanent magnet removed;

Figure 8 represents in larger scale a transverse vertical section thru the unit on the line 8--8,in Figure 1;

Figure 9 represents a top view of the unit in larger scale; i

Figure 10 represents a horizontal section `thru the central portion of the unit en the line 10-10, in Figure 6;

,Figure 11 represents in'larger scale a detail of the armature movement; and

Figure 12 represents in perspective view the intermediate transmitting lever between the armature and the cone.

Referring to Figure 1,1 represents a frame provided with a hollow circular rim 2, which may for instance be made as a sheet metal stamping or the like, the frame being suported on a base 3 to which it is attached for lnstance by the bolt 4. The central portion of the frame is suitably shaped to support'the 1926. Serial No. 112,340.

electromagnetic operating unit 5 which will hereinafter be referred to as the unit, this unit being attached to the frame in any suitable manner for instance by bolts 6 which pass thru the U-shaped permanent magnet 7-of the unit. From the unit projects the driver rod 8 which is oscillated by the armature in a manner to be described presently, and the outer end of this driver rod is attached to the cone 9 which may be of any suitable thinl material such as for instance paper, veneer or the like. rllhe driver rod 8 is adjustably attached to the apex of the cone preferably in a manner shown in Figures 4 and 5. It will be noted from these ligures that the spring chuck 10 is attached in ahole provided in the apex in the cone 9, for instance by spinning over the inner edge 11 of the chuck against-an inner and outer shield 12 preferably of metal, so that the cone material is held between these shields. The outer end of chuck 10 is longitudinally quartered by two central cuts at right angles to each other as clearly shown in Figure 5 so that the outer portion of the chuck becomes yielding, a chuck nut 13 being threaded on the outer cone shaped portion ot spring chuck 10, so that when this nut is tightened the jaws of the chuck are contracted thereby' gripping the driving rod 8 located in the central bore of the chuck.

The riml of the cone has a double reverse bendy as shown in Figure 1. The iirst reverse bend is denoted with 15 and the second reverse bend is denoted with 16. By 4these means the rim of the cone is given sufficient stiffness to keep the shape of the cone. The cone is suspended merely for the purpose of sustaining its own weight, and to take its weight olf the driving rod 8, by means of a number of tension springs 17 which are attached at their outer ends tothe inside of the hollow rim 2 of the frame and which are at their inner ends attached to the lugs 18 fastened to the cone near the edge of the firstreverse bend as shown at 19 in Figure 1. Figure 2 shows in detail the manner in which lugs 18 are attached to the cone, the lower portion 20 of lug 18 being attached, for instance by gluing, to the cone portion proper before it makes its first reverse bend. The lugs consist or' light material, for instance, as, shown in Figure 3, of fabric 21 glued between two layers 22 of paper. The frame is provided handle 23 partly shown in cross sectionin Figure 1.

The suspension of cone 9 by means of springs 17 as described, serving merely as a positioning means for the cone relatively' to the driving rod 8 of the unit and as a means for merely taking the weight of the cone ott' the driving rod, by no means .serves and is not intended to serve as an abutment for the rim of the cone. Quite to the contrarywhen in ope lation the entire cone together with its double reversed rim oscillates freely in the direction of its longitudinal axis, the slight tension of springs 17 constituting substantially no impediment to such free oscillations. In other words, the neutral position of the cone when not in operation is not determined by the springs, or at least the slight effect these springs may have in determining the neut `al position is entirelynegligible compared with the positioning effect on the cone in space which the driving rod 8 exerts,

4whose latterposition substantially alone determines the neutral position of the cone in the direction of its axis. This feature is quite important whenV comparing the cone suspension according to the present application with cones known in the prior art which are provided with a rim located-substantially in a plane at right angles to the longitudinal axis, and in which the outer edge ofy the cone rim isfattached to a ponderous. rim, so that when the cone is in operation the rim edge of the cone is stationary and so that the edge at which the cone proper joins its own rim practically performs the maximum amplitude 0scillations. In that case the normal position of the cone is largely determined by the cone rim, which, being fairly stiff, tends quite strongly to maintain the cone in a central neutral position which, after the apex of the cone has been clamped to. the driving rod, may not always coincide with the normal central position of the unit armature, incase eX- pansion 'or contraction of the cone, due to the changes in temperature or humidity, oc-r cur. In those cases an undue stress is set up which, if not relieved before the cone is operated, is apt to give rise to distortion in the sound reproduced. For example an initial stress in the outer rim is particularly harmful to reproduction of low frequencies, for which mass reactions are relatively unimportant and restoring force is the principal factor. These disadvantages are entirely avoided in the cone suspension v shown and described, on account ofthe practically negligible tendency of the peripheral springs to return the rim to a neutral position in the-direction of the cone axis.

' The unit which is shown in Figure 1 in full `View is .constructed as follows: Referring to which consists of two halves, one half being attached to each leg of the permanent magnet 7 for instance by bolts 31. A gap is provided between the inner ends or poles D-IG and 1)-15 (Figure (l) of the yokev halves between which the armature is disposed as will be described presently. In order to conveniently hohl the pack of laminac. of which the yoke is composed, together, so that the mamifarture in quantity is facilitated, a top plate 3i. and a bottom plate 33 of non-magnetic material is provided which bridge the two halves of the yoke, each plate being provided with rectangular slots 34 (Figure 9) which engage with a presstit protruding lugs 35 of the yoke may readily be seen from Figure 6. The two plates 32 and 33 are held together by two, stay bolts 3G which are more clearly visible in Figures 7 and 8. By this arrangement not only are`the lamime tightly held together but at the same time the gaps D-E and D-E are very exactly determined. The pole ends of the yoke halves are provided with inward lugs 37 clearly visible in Figure 6 which serve for centering the operating current coils 38 and 39 with relation to the gaps DME and D-E. These coils, which may be connected in series or in parallel as the construction of the unit may require, may be conveniently inserted in place,

ltogether and inserting them into the yoke,

their combined length being less than the distance between the lugs 37 appel-taining to each yoke half. After the coils are inserted, they are spread apart by means of wedges 40 so thatthey are seated over the respective lugs 37 and permanently held in place.

The armature 41 whichv is placed between the gaps of the yoke is of elongated diamond shape as may be seen in 'detail in Figures 6 and 11, and is also composed of a suitable number` of laminae which are held together by small rivets 42. This shape is of particular advantage, because its greatest mass is near its central portion where it least affects the frequencies at which the armature tends to oscillate, the outer tapered ends being comparatively thin and light, yet sufficient in cross section to carry the necessary magnetic flux.

The armature laminae are provided with a cential transverse slot 43 into which, after the armature laminae are assembled and riveted, a flat torsionally yielding bar 44 is pressed which preferably consists ofphosplier-bronze. Also this construction is of particular advantage for armatures of this type over prior constructions in which the yielding element, such as a flat bar, surrounds the armature. In that case the alternating flux longitudinally traversing the armature is apt to setup eddy currents which encircle the armature iii the bar, giving rise to notinconsiderable energy losses. When the bar passes through the armature as shown here these currents cannot be set up.

The bar is visible in plan view in Figure l() and, as will be noted from that ligure, is provided with a shoulder 45 against which the armature 41 rests after it has been pressed onto the bar. It may be noted that,4 for convenience of correctly assembling the armature laminas so as to avoid the cii'ectof slight discrepancies in symmetry between the two ends of the armature which may have been caused hy inaccuracies in the dies used for punching the laminae, ll have provided a small notch 46 (see Figure 11) on each lamina and when the laminas are assembled they are lined up so as to register at their notches 46, whereby all upper and lower ends of the diamond come together the same way as they are punched.

Armature bar 44 is disposed transverse to the plane of magnet yoke 30 and is supported at its two ends on studs which are attached to the non-magnetic end plates 32 and 33 of the yoke. As will be noted for instance from Figure 8 one end ot armature bar 44 is attached to astud 5,0 fastened to the upper yoke plate 32, and the'other end of the bar is at tached to a stud 51 fastened to the lower yoke plate 33. ln placing the armature bar on its studs the armature is carefully centered so that its upper and lower end is symmetrically located in the air gaps D-E and D-F/ of the yoke. r

By arranging the yoke and the armature of the unit in the manner described I avoid entirely the passing of the flux produced by the operating current thru the Shanks of the permanent steel magnet 7. The flux which prevails in this arrangement is as follows: The permanent flux prevailing in the permanent magnet 7 for instance passes in the direction of the full line arrows from A over B into the laminated yoke arm by way of D', across the'air gaps and the armature end to E and over G in the direction of H. Also from A byfway of C, D, air gaps and upper armature end E, F, G, in the direction of H. With this flux prevailing and no operating current flowing thru the yoke coils 38, 39, it will be noted that the armature is completely balanced in its position in the yoke and no torsion is exerted on armature bar 44. It now fluctuating operating current flows thru coils 38 and 39, the iux, set up by these coils only travels thru the yoke, and taking one time instance of the flow, we may assume that it flows in the direction of the dotted` line ar rows. It would thus flow from B over C, D into the upper end of the armature, thru the 4length of the armature to D and back to B.

Also fromY G to F, E into the u )per end of the armature and thru its length to E and back to G. Considering now that the permanent ilux be in the direction as assumed hereinbet'ore, this permanent flux is at the time the forces produced by theoperating flux are i effective simultaneously and symmetrically at both ends of the armature, tending to rock it to and fro by distorting armature bar 40, which normally tends to return the armature into the central position shown in Figure 6.

The oscillations performed by the armature due to the operating current are transmitted to the cone as follows. As will be noted from Figures 8, 9 and 11 the outermost lamina 41 on one side oi' the upper end of the armature is made of easysolderable material and this lamina is slightly outward bent and curved at its end as shown at 6() and to the curved portion .is attached, for instance by bi'azing, an operating rod 61 more clearly shown in Figure 1l. .This operating rod is brazed at its other end 62 to the free end of an L-shaped reducing element 63. This element is shown in perspective view in detail in Figure l2 and consists of a flat portion 64 with outwardly turned edges 65 to give it the necessary stiffness, and ot' a base portion 66 likewise having outwardly turned edges 67 to give it the necessary stiffness. At the bent portion 68, no lateral out-turned edges are provided so that the element will yield at this portion to any bending forces applied at the upper free end 62 when its lower or base portion 66 is held in fixed position.

It should be noted however' that the lateral flanges 65 must extend very close to the bend 68, so that portion 64 may at no point be able to whip in the direction in which rod (3l cxtends and vibraties. This might easily occur at higher tone frequencies if flanges 65 do not extend to the bend, and would thereby iutroduce energy losses and distortions.

The base portion 66 is attached to the 'lower yoke plate 33 by means of a screw 69, a small detent 70 provided at the end of base por tion 66 engaging in a notch 71 punched into lower yoke plate 33 by which the turning of the reducing element 63 on screw 69 is prevented. Portion 64 of this element has fixed to it intermediate its ends in suitable manner, for instance by brazing, the driver rod 8, the outer end of Whichis attached to the cone apex as described at the beginning.

Over the driver rod isslippe'd preferably a piece of rubber tubing 73 which extends substantially the full length of driver rod 8 and tends to dampen the transverse vibrations whicli the rod 8 may be inclined to perform and which are apt to distort the sound produced.

The lead by which the operating current is supplied to coils 38 and 39 may be attached to a binding post strip attached to the per= manent magnet 7 across its two shanks, the binding posts being shown at 76. The flexible current supply cord 77 is guided thru an eye 78 provided in the frame portion of the loud speaker and the entire unit is surrounded by a casing 7 9 by which it is protected from dust, the driver rod 8 carrying the rubbe1"damper 73 passing thru a hole 8() out of the casing.

I claim 1. An electromagnetic sound reproducing unit having a laminated yoke comprising two halves facing each other with their pole ends and having gaps between opposing pairs of poles and an armature disposed in said gaps, said yoke halves having lugs on the sides of their shanks and non-magnetic end plates having recesses to engage the lugs of opposing voke Shanks thereby securing the exact size of the gap between them. y

Q. An electromagnetic sound reproducing unit having -a laminated yoke comprising two halves facing each other with their pole ends and having gaps between opposing pairs of poles and an armature disposed in said gaps,

said yoke halves having lugs on the outward sides of their Shanks and non-magnetic end plates having recesses to engage the lugs of opposing yoke Shanks thereby securing the exact size of the gap between them, and stay bolts for holding said plates together.

3. An electromagnetic sound reproducing unit having a laminated yoke comprising two U-shaped halves facing each other with their pole ends and h'aving a gap between each opposing pair of poles and an armature disposed with its ends in said gaps, said yoke halves having lugs on the outward sides of their shanks and non-magnetic end plates having recesses to engage the lugs of opposing yoke Shanks, thereby fixing the spacing between opposing yoke poles, and stay-bolts for holding said end plates together, a torsionally yielding bar supporting said armature.

freely within said yoke gaps and extending through said armature in the direction of the central transverse armature axis, one end of said bar being secured vto one end plate and the other end being secured to the other endplate.

4. An electromagnetic sound reproducing unit having` a yoke comprising two halves facing each other with their pole ends and having gaps between opposing pairs of poles and an armature oscillatingly supported intermediate its ends and being disposed in said gaps, said armature having an elongated diamond shape, the thin tapered ends of the armature being disposed in said gaps, and the pole ends of said yoke halves being shaped to substantially follow the lcontour of Said tapered ends.

5. An electromagnetic sound reproducing unit having ayoke, poles thereon, an oscillating armature extending between said poles to conduct the magnetic flux between said poles, a yielding supporting bar extending through said armature transversely to its longitudinal axis to permit the armature to oscillate on said bar, said magnetic iiux passing around both sides of said bar.

6. An electromagnetic sound reproducing unit having a yoke comprising two halves facing each other with their pole ends and having gaps between opposing pairs of poles, and an elongated diamond shaped armature disposed with its thin tapered ends in said gaps to oscillate therein and adapted to conduct the magnetic iiux between the yoke poles, a torsionally yielding bar of non-magnetic material passing thru the center of the armature in a direction transversely ot the longitudinal armature axis, thereby oscillatingly supporting the armature, said magnetic iux passing symmetrically around both sides of said bar.

7. An electromagnetic sound reproducing unit having a yoke, poles thereon, a laminated oscillatory armature extending between said yoke poles and means for oscillatingly supporting said armature midway between said ends, said armature having the outermost lamina at one side consisting of an easily brazable metal, the end of said lamina being bent away from the armature body. and a transmitting rod brazed tosaid lamina end for transmitting the oscillations of said armature.

8. An electromagnetic sound reproducing unit having an oscillating armature, a sound 'radiator operated by said armature and a motionamplitude reducing means disposed between said armature and said radiator, said reducing means comprising an L-shaped lever element having lateral flanges at both of its shanks, one shank being rigidly held,

a transmitting rod fixed at one end to said l,

armature and at the other end to the outer end of the free shank of said lever element, and an operating rod fixed at one end 'to said free shank intermediate its ends, and at the other end to sai-d radiator, the flanges of said tree shank extending close to the bend of the lever element to prevent whipping of the free shank during the oscillations.

9. An electromagnetic sound reproducing unit having a laminated yoke comprising two halves whose Shanks face each other endwise to form opposing poles and having gapsbetween opposing pairs of'poles and non -rnagnetic positioning elements extending across each pair of opposing Shanks and engaging said slianks to tix and maintain the exact size of said gaps. v

10. An electromagnetic sound reproducing unit having a yoke and poles thereon and an elongated armature element oscillatingly supported intermediate its ends and being tapered at both ends and disposed with said ends adjacent to said poles, said poles being shaped to substantially follow the contour of said tapered ends.

11. An elevlromagnotic sound reproducing unit having a yoke and poles thereon and au elongated ai'inatlu'o element, tapered at its @nils and iliifposoil across said poles to conduct the magnetic flux between said poles, a torsionally x,'ieliliug bar of non-magnetic material passing through he center of said armature in a direction transversely of the longitudinal armature axis for oscllatiugly supporting said armature, said magnetic fiux passing symmetrically around both sides of said bar.

LAZARUS SHAPRG. 

